Lubricant compositions for transmissions

ABSTRACT

The present disclosure relates to a lubricating composition including at least one base oil, at least one compound including a dithiocarbamate group, at least one compound including a phosphite group, at least one compound including a dithiophosphate group and at least one compound including a thiadiazole group. The lubricating composition simultaneously exhibits good anti-wear properties, extreme-pressure, a low friction coefficient and good anti-seizing properties. The lubricating composition can be used for lubricating transmissions such as gearboxes, axles, preferably manual gearboxes of motor vehicles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Entry of International Patent Application No. PCT/EP2014/066596, filed on Aug. 1, 2014, which claims priority to French Patent Application Serial No. 13 57 713, filed on Aug. 2, 2013, both of which are incorporated by reference herein.

FIELD

The present invention is applicable to the field of lubricants, and more particularly to the field of lubricants for motor vehicles, in particular to the field of lubricants for motor vehicle transmission components, in particular for manual gearboxes, axles or dual clutches. The invention relates to a lubricating composition comprising the combination of phosphorus-, sulphur- and phosphorus and sulphur-containing compounds with a corrosion inhibitor, as well as its preparation method. The lubricating composition according to the invention exhibits, in particular, good extreme-pressure and anti-wear properties, more particularly vis-à-vis the synchronizers present in the gearboxes, as well as a low friction coefficient.

The present invention also relates to a method for reducing the wear of a mechanical part utilizing this lubricating composition. The present invention also relates to a method for reducing the seizing of a mechanical part utilizing this lubricating composition. The present invention also relates to a method for reducing the flaking of a mechanical part utilizing this lubricating composition. The present invention also relates to a standard additives-concentrate composition comprising the combination of phosphorus-, sulphur- and phosphorus and sulphur-containing compounds with a corrosion inhibitor.

BACKGROUND

It is very difficult to formulate lubricating compositions simultaneously having good extreme-pressure properties, good anti-wear properties and good friction properties, as well as good anti-seizing properties. Thus most of the lubricating compositions have only two of these properties at once. Moreover, despite the existence of a large number of anti-wear additives, extreme-pressure additives or friction-modifying additives, not all have the same effectiveness, some being able to improve one property and at the same time make a second property worse. Similarly, the chemistry of these additives is complex and the additives can react with each other to form new chemical species the influence of which on the extreme-pressure, wear, friction and seizing properties is ultimately unknown.

It is known that additives such as the diphosphites, which can be both friction modifiers and anti-wear components, react with the sulphur atoms contained in the extreme-pressure additives to form for example thiophosphonic derivatives, the properties of which are markedly different from those of the original molecules. Thus, a large number of extreme-pressure components react with the anti-wear additives or the friction modifiers in order to produce novel chemical entities. These reactions are not controlled, nor are the precise properties of the final product monitored over time. Interactions can occur between the different extreme-pressure/anti-wear additives/friction modifiers and lead to antagonistic effects on the final properties of the compositions containing additives.

The documents US 2009/011964, U.S. Pat. No. 5,674,820 and U.S. Pat. No. 5,872,085 describe a lubricating composition comprising a compound comprising a dithiocarbamate group, a compound comprising a phosphite group and a compound comprising a dithiophosphate group. However, the presence of a compound comprising a dithiophosphate group may lead to significant wear of the synchronizers. Moreover, these documents do not describe the presence of a thiadiazole-type compound.

Wear of the synchronizers present in a gearbox, and more particularly in manual gearboxes, is a significant and recurring problem. This type of wear in particular involves contacts other than steel/steel contacts, such as for example steel/brass contacts. Lubricating compositions making it possible to reduce wear of the synchronizers have been described.

Thus, document WO 03/035810 describes a lubricating composition comprising a base oil, an amine salt of a phosphorus-containing acid, a metal salt of an organic acid. Moreover, the lubricating composition can also comprise a metal deactivator compound, which can be a dimercaptothiadiazole compound and a boron-based dispersant. However, this document does not describe the presence of compounds comprising a dithiocarbamate group or compounds comprising a dithiophosphate group. Furthermore, the lubricating composition described in this document must comprise less than 0.1% by weight of anti-wear/extreme-pressure non-metallic and sulphur-containing compounds, which can correspond to compounds comprising a dithiocarbamate group or to compounds comprising a dithiophosphate group.

It would therefore be desirable to have available a lubricating composition, in particular for motor vehicles, which simultaneously have good extreme-pressure, friction and anti-wear properties, in particular vis-à-vis synchronizers, as well as good anti-seizing properties. It would also be desirable to have available a lubricating composition, in particular for motor vehicles, which is both stable and which has good extreme-pressure, friction, anti-wear and anti-seizing properties. It would also be desirable to have available a lubricating composition, in particular for motor vehicles, which limits the risks of flaking and which has good extreme-pressure, friction, anti-wear and anti-seizing properties.

An objective of the present invention is to provide a lubricating composition overcoming all or some of the abovementioned drawbacks. Another objective of the invention is to provide a lubricating composition that is stable and easy to utilize. Another objective of the invention is to provide a lubricating method making it possible in particular to reduce the wear of the synchronizers in the gearboxes.

SUMMARY

An object of the invention is thus a lubricating composition comprising:

-   -   at least one base oil,     -   at least one compound A comprising a dithiocarbamate group,     -   at least one compound B comprising a phosphite group,     -   at least one compound C comprising a dithiophosphate group, and     -   at least one compound D comprising a thiadiazole group,     -   compound A comprising a dithiocarbamate group being a mixture         of:         -   at least one amine dithiocarbamate of general formula (I)             (compound A-1)

wherein

-   -   R₁ and R₂ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms,     -   R₃, R₄ and R₅ represent independently of each other a hydrogen         atom or a hydrocarbon-containing group of 1 to 30 carbon atoms,         it being understood that at least one of the R₃, R₄ and R₅         groups is not a hydrogen atom, and         -   at least one metal dithiocarbamate of general formula (II)             (compound A-2)

-   -   wherein R₆ and R₇ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms, M represents a metal         cation and n is the valency of this metal cation,         -   compound D comprising a thiadiazole group being selected             from the group formed by:             -   a compound of Formula (V-a)

wherein:

-   -   R₂₇ and R₂₈, identical or different, represent independently a         hydrogen atom or a linear or branched, saturated or unsaturated,         alkyl group, comprising from 1 to 30 carbon atoms,     -   a represents an integer ranging from 1 to 3,     -   b represents an integer ranging from 1 to 3,         -   a compound of Formula (V-b)

wherein

-   -   R₂₈ represents a hydrogen atom or a linear or branched,         saturated or unsaturated, alkyl group, comprising from 1 to 30         carbon atoms,     -   b represents an integer ranging from 1 to 3,         -   a mixture of at least one compound of Formula (V-a) and at             least one compound of Formula (V-b),

the ratio by weight (compound C comprising a dithiophosphate group: compound D comprising a thiadiazole group) ranging from 5:1 to 1:10.

Surprisingly, the applicant has noted that the presence of at least one compound comprising a dithiophosphate group, at least one compound comprising a phosphite group, at least one compound comprising a dithiocarbamate group in the form of a specific mixture of a compound of Formula (I) and a compound of Formula (II) and at least one compound comprising a thiadiazole group selected from the group formed by a compound of Formula (V-a), a compound of Formula (V-b) and a mixture of at least one compound of Formula (V-a) and at least one compound of Formula (V-b), in a lubricating composition makes it possible to confer upon the lubricating composition, simultaneously, good extreme-pressure, friction and anti-wear properties, in particular vis-à-vis synchronizers, as well as good anti-seizing properties. Thus, the present invention makes it possible to formulate lubricating compositions comprising a reduced content of compounds comprising a dithiophosphate group and exhibiting, however, remarkable extreme-pressure, friction, anti-wear and anti-seizing properties.

Advantageously, the lubricating compositions according to the invention have improved anti-wear properties vis-à-vis the synchronizers present in gearboxes. Advantageously, the lubricating compositions according to the invention also have good anti-flaking properties. Advantageously, the lubricating compositions according to the invention also have good anti-oxidant and corrosion inhibiting properties. Advantageously, the lubricating compositions according to the invention exhibit improved storage stability as well as a viscosity that does not vary, or varies very little.

In an embodiment of the invention, the lubricating composition essentially consists of:

-   -   at least one base oil,     -   at least one compound A comprising a dithiocarbamate group,     -   at least one compound B comprising a phosphite group,     -   at least one compound C comprising a dithiophosphate group, and     -   at least one compound D comprising a thiadiazole group,         compound A comprising a dithiocarbamate group being a mixture         of:     -   at least one amine dithiocarbamate of general formula (I)         (compound A-1)

wherein

-   -   R₁ and R₂ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms,     -   R₃, R₄ and R₅ represent independently of each other a hydrogen         atom or a hydrocarbon-containing group of 1 to 30 carbon atoms,         it being understood that at least one of the R₃, R₄ and R₅         groups is not a hydrogen atom, and     -   at least one metal dithiocarbamate of general formula (II)         (compound A-2),

-   -   wherein R₆ and R₇ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms, M represents a metal         cation and n is the valency of this metal cation,         -   compound D comprising a thiadiazole group being selected             from the group formed by:             -   a compound of Formula (V-a)

-   -   R₂₇ and R₂₈, identical or different, represent independently a         hydrogen atom or a linear or branched, saturated or unsaturated,         alkyl group, comprising from 1 to 30 carbon atoms,     -   a represents an integer ranging from 1 to 3,     -   b represents an integer ranging from 1 to 3,         -   a compound of Formula (V-b)

wherein

-   -   R₂₈ represents a hydrogen atom or a linear or branched,         saturated or unsaturated, alkyl group, comprising from 1 to 30         carbon atoms,     -   b represents an integer ranging from 1 to 3,         -   a mixture of at least one compound of Formula (V-a) and at             least one compound of Formula (V-b),

the ratio by weight (compound C comprising a dithiophosphate group: compound D comprising a thiadiazole group) ranging from 5:1 to 1:10.

The invention also relates to a method for preparing a lubricating composition as defined above. The invention also relates to an oil for transmissions comprising a lubricating composition as defined above. The invention also relates to the use of a lubricating composition as defined above for the lubrication of transmissions such as gearboxes or axles, preferentially gearboxes of motor vehicles, advantageously for the lubrication of manual gearboxes.

The invention also relates to the use of a lubricating composition according to the invention in order to reduce the fuel consumption of vehicles, in particular of motor vehicles. The invention also relates to the use of a lubricating composition according to the invention for reducing the seizing of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox. The invention also relates to the use of a lubricating composition according to the invention for reducing the wear of a gearbox synchronizer, preferentially of manual gearboxes.

The invention also relates to the use of a lubricating composition according to the invention for reducing the flaking of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox. The invention also relates to a method for lubricating transmissions such as the gearboxes, the axles, preferably manual gearboxes of motor vehicles, said process comprising at least one step of bringing into contact with the lubricating composition according to the invention. The invention also relates to a method for reducing the seizing of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox, comprising at least bringing the mechanical part into contact with a lubricating composition according to the invention. The invention also relates to a method for reducing the wear of a gearbox synchronizer, preferentially of manual gearboxes, comprising at least bringing the synchronizer into contact with a lubricating composition according to the invention. The invention also relates to a method for reducing the flaking of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox, comprising at least bringing the mechanical part into contact with a lubricating composition according to the invention.

The invention also relates to the use of at least one compound A comprising a dithiocarbamate group, at least one compound B comprising a phosphite group, at least one compound C comprising a dithiophosphate group and at least one compound D comprising a thiadiazole group in a base oil for improving the anti-wear, extreme-pressure, friction and anti-seizing properties of a lubricating composition, compound A comprising a dithiocarbamate group being a mixture of:

-   -   at least one amine dithiocarbamate of general formula (I)         (compound A-1)

wherein

-   -   R₁ and R₂ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms,     -   R₃, R₄ and R₅ represent independently of each other a hydrogen         atom or a hydrocarbon-containing group of 1 to 30 carbon atoms,         it being understood that at least one of the R₃, R₄ and R₅         groups is not a hydrogen atom, and         -   at least one metal dithiocarbamate of general formula (II)             (compound A-2),

-   -   wherein R₆ and R₇ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms, M represents a metal         cation and n is the valency of this metal cation,     -   compound D comprising a thiadiazole group being selected from         the group formed by:         -   a compound of Formula (V-a)

wherein:

-   -   R₂₇ and R₂₈, identical or different, represent independently a         hydrogen atom or a linear or branched, saturated or unsaturated,         alkyl group, comprising from 1 to 30 carbon atoms,     -   a represents an integer ranging from 1 to 3,     -   b represents an integer ranging from 1 to 3,         -   a compound of Formula (V-b)

wherein

-   -   R₂₈ represents a hydrogen atom or a linear or branched,         saturated or unsaturated, alkyl group, comprising from 1 to 30         carbon atoms,     -   b represents an integer ranging from 1 to 3,         -   a mixture of at least one compound of Formula (V-a) and at             least one compound of Formula (V-b).

The invention also relates to a composition of the additives-concentrate type comprising:

-   -   at least one compound A comprising a dithiocarbamate group,     -   at least one compound B comprising a phosphite group,     -   at least one compound C comprising a dithiophosphate group, and     -   at least one compound D comprising a thiadiazole group.

DETAILED DESCRIPTION

The percentages given below correspond to percentages by mass of active ingredient.

Dithiocarbamate

The lubricating composition according to the invention comprises at least one compound A comprising a metal dithiocarbamate group and at least one compound comprising an amine dithiocarbamate group. With a view to simplification of the description, the compound comprising a metal dithiocarbamate group is called “metal dithiocarbamate” and the compound comprising an amine dithiocarbamate is called “amine dithiocarbamate” in the remainder of the present description. The metal dithiocarbamate is a metal dithiocarbamate of general formula (II) (compound A-2), wherein R₆ and R₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, M represents a metal cation and n is the valency of this metal cation:

Preferably, the metal is selected from the group constituted by zinc, aluminium, copper, iron, mercury, silver, cadmium, tin, lead, antimony, bismuth, thallium, chromium, molybdenum, cobalt, nickel, tungsten, sodium, calcium, magnesium, manganese and arsenic. In a preferred embodiment of the invention, the metal is selected from zinc, molybdenum and antimony, preferably zinc and molybdenum, preferably zinc. Mixtures of metals can be used. The metal dithiocarbamates are neutral as represented in Formula (II) or basic when a stoichiometric excess of metal is present.

Preferably, R₆ and R₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms. In a preferred embodiment of the invention, R₆ and R₇ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. The alkyl, alkenyl, alkynyl, aryl groups comprise from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms.

In another preferred embodiment of the invention, R₆ and R₇ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms. In another preferred embodiment of the invention, R₆ and R₇ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more heteroatoms such as the oxygen atom, nitrogen atom, sulphur atom, phosphorus atom, preferably with one or more oxygen atoms.

The metal dithiocarbamates that can be used are compounds well known to a person skilled in the art. One of the methods for preparing these compounds is described in the U.S. Pat. No. 2,492,314. Suppliers of such additives are for example Vanderbilt, Rhein Chemie, Adeka, King Industries.

Commercial compounds are for example Vanlube® AZ, Vanlube® EZ, Vanlube® 73, Vanlube® 73 Super Plus, Molyvan® A, Molyvan® 807, Molyvan® 822, Additin® RC 6301, Additin® RC 6320, Sakura-Lube® 200, Sakura-Lube® 165, Sakura-Lube® 525, Sakura-Lube® 600, Na-Lube® ADTC. These compounds are marketed in particular by one of the abovementioned suppliers.

In a preferred embodiment of the invention, the metal dithiocarbamate is a zinc dithiocarbamate of Formula (II-a), wherein R₆ and R₇ have the same meaning as in Formula (II):

Particularly preferred compounds corresponding to Formula (II-a) are such that R₆ and R₇ represent independently of each other linear alkyl hydrocarbon-containing groups comprising from 4 to 12 carbon atoms and are for example, zinc diamyldithiocarbamate and zinc dibutyldithiocarbamate.

In another preferred embodiment of the invention, the metal dithiocarbamate is a molybdenum dithiocarbamate of Formula (II-b), wherein R₆ and R₇ have the same meaning as in Formula (II):

The amine dithiocarbamate is an amine dithiocarbamate of general formula (I), wherein R₁ and R₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, R₃, R₄ and R₅ represent independently of each other a hydrogen atom or a hydrocarbon-containing group of 1 to 30 carbon atoms, it being understood that at least one of the R₃, R₄ and R₅ groups is not a hydrogen atom:

In a preferred embodiment of the invention, R1 and R2 represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms. In another preferred embodiment of the invention, R₁ and R₂ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. These alkyl, alkenyl, alkynyl, aryl groups comprise from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms.

In another preferred embodiment of the invention, R₁ and R₂ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms. In another preferred embodiment of the invention, R₁ and R₂ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more heteroatoms such as the oxygen atom, the nitrogen atom, the sulphur atom, the phosphorus atom, preferably with one or more oxygen atoms. In another preferred embodiment of the invention, R₃, R₄ and R₅ represent independently of each other a hydrocarbon-containing group comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 4 to 12 carbon atoms.

Particularly preferred compounds are diamyl amine diamyldithiocarbamate and diamyl amine dibutyldithiocarbamate. Commercial compounds are for example Vanlube® EZ marketed by the company Vanderbilt. In a more preferred embodiment of the invention, the dithiocarbamate is a mixture of at least one amine dithiocarbamate of general formula (I) and at least one metal dithiocarbamate of general formula (II-a) described above.

Advantageously, the dithiocarbamate is a mixture of zinc dithiocarbamate and diamyl ammonium diamyldithiocarbamate. In an embodiment, the composition according to the invention can also comprise another compound comprising a dithiocarbamate group different from a dithiocarbamate of Formula (I) or of a dithiocarbamate of Formula (II). In a preferred embodiment of the invention, this other compound comprising a dithiocarbamate group is selected from the group constituted by the bisdithiocarbamates, ammonium dithiocarbamates and ester dithiocarbamates, used alone or in a mixture.

In a first embodiment, this other dithiocarbamate compound is a bisdithiocarbamate of general formula (VI-a), wherein R₂₉, R₃₀, R₃₁ and R₃₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, R₃₃ represents a hydrocarbon-containing group of 1 to 8 carbon atoms:

In a preferred embodiment of the invention, R₂₉, R₃₀, R₃₁ and R₃₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₂₉, R₃₀, R₃₁ and R₃₂ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₂₉, R₃₀, R₃₁ and R₃₂ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups.

In another preferred embodiment of the invention, R₂₉, R₃₀, R₃₁ and R₃₂ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably one or more oxygen atoms. In another preferred embodiment of the invention, R₃₃ represents a hydrocarbon-containing group of 2 to 6 carbon atoms. Commercial compounds are for example Vanlube® 7723 marketed by the company Vanderbilt or Additin® RC 6340 marketed by the company Rhein Chemie.

In a second embodiment, this other dithiocarbamate compound is an ammonium dithiocarbamate of general formula (VI-b), wherein R₃₄ and R₃₅ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms:

In a preferred embodiment of the invention, R₃₄ and R₃₅ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₃₄ and R₃₅ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₃₄ and R₃₅ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups. In another preferred embodiment of the invention, R₃₄ and R₃₅ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms.

In a third embodiment, this other dithiocarbamate compound is a dithiocarbamate ester of general formula (VI-c), wherein R₃₆ and R₃₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, R₃₈ and R₃₉ represent independently of each other hydrocarbon-containing groups comprising from 1 to 18 carbon atoms:

In a preferred embodiment of the invention, R₃₆ and R₃₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₃₆ and R₃₇ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₃₆ and R₃₇ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups.

In another preferred embodiment of the invention, R₃₆ and R₃₇ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms. In another preferred embodiment of the invention, R₃₈ and R₃₉ represent independently of each other hydrocarbon-containing groups of 2 to 6 carbon atoms. In an embodiment of the invention, the lubricating composition comprises from 0.1 to 5% by mass of compounds A comprising a dithiocarbamate group, relative to the total mass of lubricating composition, preferably from 0.2 to 4%, more preferentially from 0.3 to 2%, advantageously from 0.5 to 1%. In another embodiment of the invention, the lubricating composition comprises from 0.1 to 3% by mass of the mixture of amine dithiocarbamate corresponding to Formula (I) (compound A-1) and metal dithiocarbamate corresponding to Formula (II) (compound A-2), preferably from 0.1 to 2% by mass, advantageously from 0.5 to 2% by mass, relative to the total mass of the lubricating composition.

Phosphite

The lubricating composition according to the invention comprises at least one compound B comprising a phosphite group. With a view to simplification of the description, compound B comprising a phosphite group is called “phosphite” in the remainder of the present description. In an embodiment of the invention, the phosphite is selected from the phosphite monoesters, the phosphite diesters or the phosphite triesters, used alone or in a mixture. The phosphite monoesters are found in two forms in equilibrium, a “ketone” form and an “alcohol” form. The same is true of the phosphite diesters.

In an embodiment of the invention, the phosphite can be a phosphite monoester of general formula (III-a) in its alcohol and/or ketone form, wherein R₈ represents a hydrocarbon-containing group, optionally substituted, comprising from 1 to 30 carbon atoms:

In a preferred embodiment of the invention, R8 represents a hydrocarbon-containing group, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 20 carbon atoms, even more preferentially from 4 to 18 carbon atoms, even more preferentially from 6 to 16 carbon atoms, even more preferentially from 8 to 15 carbon atoms. In another preferred embodiment of the invention, R₈ represents an unsubstituted hydrocarbon-containing group, said hydrocarbon-containing group being able to be an alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl, group. In another preferred embodiment of the invention, R₈ represents a linear or branched alkyl hydrocarbon-containing group, more preferentially a linear alkyl hydrocarbon-containing group. In another preferred embodiment of the invention, R₈ represents a hydrocarbon-containing group substituted with oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably oxygen atoms.

In another embodiment of the invention, the phosphite can also be a phosphite diester of general formula (III-b) in its alcohol and/or ketone form, wherein R₉ and R₁₀ represent independently of each other hydrocarbon-containing groups, optionally substituted, of 1 to 30 carbon atoms:

In a preferred embodiment of the invention, R₉ and R₁₀ represent hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 20 carbon atoms, even more preferentially from 4 to 18 carbon atoms, even more preferentially from 6 to 16 carbon atoms, even more preferentially from 8 to 12 carbon atoms. In another preferred embodiment of the invention, R₉ and R₁₀ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₉ and R₁₀ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups.

In another preferred embodiment of the invention, R₉ and R₁₀ represent hydrocarbon-containing groups substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms. As examples of phosphite diesters, dimethyl phosphite, diethyl phosphite, diisopropyl phosphite, dibutyl phosphite, dihexyl phosphite, dicyclohexyl phosphite, diisodecyl phosphite, di-n-octyl phosphite, dibenzyl phosphite, diphenyl phosphite, and dioleyl phosphite may be mentioned.

In an embodiment of the invention, the phosphite can also be a phosphite triester of general formula (III-c) wherein R₁₁, R₁₂ and R₁₃ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms:

In a preferred embodiment of the invention, R₁₁, R₁₂ and R₁₃ represent hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 20 carbon atoms, even more preferentially from 4 to 18 carbon atoms, even more preferentially from 6 to 16 carbon atoms, even more preferentially from 8 to 12 carbon atoms. In another preferred embodiment of the invention, R₁₁, R₁₂ and R₁₃ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₁₁, R₁₂ and R₁₃ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups. In another preferred embodiment of the invention, R₁₁, R₁₂ and R₁₃ 27 Clean Specification represent hydrocarbon-containing groups substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably one or more oxygen atoms.

As examples of phosphite triesters, diphenyl isodecyl phosphite, diphenyl isooctyl phosphite, tridimethylphenyl phosphite, diphenyl ethylhexyl phosphite, phenyl diisodecyl phosphite, triisodecyl phosphite, trilauryl phosphite, triphenyl phosphite, tris(dipropyleneglycol) phosphite, tris(nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(5-norbornene-2-methyl) phosphite, tris(tridecyl) phosphite, trimethyl phosphite, triethyl phosphite, triisopropyl phosphite, tributyl phosphite, triisoctyl phosphite, tribenzyl phosphite, triphenyl phosphite, poly(dipropyleneglycol) phenyl phosphite or tris(dipropylene glycol) phosphite may be mentioned. Commercial compounds are for example Duraphos® AP230, Duraphos® AP240L, Duraphos® DBHP, Doverphos® 4, Doverphos® 10, Doverphos® 213, Doverphos® 6, Doverphos® 7, Doverphos® 8, Doverphos® 9, Doverphos® 11, Doverphos® 12, Doverphos® 613, Doverphos® 675, Doverphos® 49, Doverphos® 53, Doverphos® 72, Doverphos® 253, Doverphos® 271, Irgaphos® OPH, or the Rhodaphos® range products marketed by the company Rhodia. In an embodiment of the invention, the lubricating composition comprises from 0.1 to 5% by mass of phosphite, relative to the total mass of the lubricating composition, preferably from 0.2 to 4%, more preferentially from 0.3 to 2%, even more preferentially from 0.5 to 1%.

Dithiophosphate

The lubricating composition according to the invention comprises at least one compound C comprising a dithiophosphate group. With a view to simplification of the description, compound C comprising a dithiophosphate group is called “dithiophosphate” in the remainder of the present description. In an embodiment of the invention, the dithiophosphate can be selected from the group constituted by the ammonium dithiophosphates, amine dithiophosphates, ester dithiophosphates and metal dithiophosphates, used alone or in a mixture. The ammonium dithiophosphates, amine dithiophosphates and ester dithiophosphates have the advantage of being ashless dithiophosphates, in particular zinc-free.

In a first embodiment, the dithiophosphate is an ammonium dithiophosphate of general formula (IV-a),

wherein R₁₄ and R₁₅ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms.

In a preferred embodiment of the invention, R₁₄ and R₁₅ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₁₄ and R₁₅ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₁₄ and R₁₅ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups.

In another preferred embodiment of the invention, R₁₄ and R₁₅ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms. As examples of dithiophosphates, the ammonium dimethyl dithiophosphates, ammonium diethyl dithiophosphates, or ammonium dibutyl dithiophosphates may be mentioned.

In a second embodiment, the dithiophosphate is an amine dithiophosphate of general formula (IV-b), wherein R₁₆ and R₁₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, R₁₈, R₁₉ and R₂₀ represent independently of each other a hydrogen atom or a hydrocarbon-containing group of 1 to 30 carbon atoms, it being understood that at least one of the R₁₈, R₁₉ and R₂₀ groups is not a hydrogen atom:

In a preferred embodiment of the invention, R₁₆ and R₁₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₁₆ and R₁₇ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In a preferred embodiment of the invention, R₁₆ and R₁₇ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups.

In a preferred embodiment of the invention, R₁₆ and R₁₇ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms. In a preferred embodiment of the invention, R₁₈, R₁₉ and R₂₀ represent independently of each other a hydrocarbon-containing group comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. Commercial compounds are for example Additin® RC 3880 marketed by the company Rhein Chemie.

In a third embodiment, the dithiophosphate is an ester dithiophosphate of general formula (IV-c), wherein R₂₁ and R₂₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, R₂₃ and R₂₄ represent independently of each other hydrocarbon-containing groups comprising from 1 to 18 carbon atoms:

In a preferred embodiment of the invention, R₂₁ and R₂₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₂₁ and R₂₂ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₂₁ and R₂₂ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups.

In another preferred embodiment of the invention, R₂₁ and R₂₂ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms. In another preferred embodiment of the invention, R₂₁ and R₂₂ represent independently of each other, a hydrocarbon-containing group of 2 to 6 carbon atoms. In another preferred embodiment of the invention, R₂₃ and R₂₄ represent independently of each other hydrocarbon-containing groups comprising from 2 to 6 carbon atoms. Commercial compounds are for example Irgalube® 63 marketed by the company BASF.

In a fourth embodiment, the dithiophosphate is a metal dithiophosphate of general formula (IV-d), wherein R₂₅ and R₂₆ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, M represents a metal cation and n is the valency of this metal cation:

In a preferred embodiment of the invention, the metal is selected from the group constituted by zinc, aluminium, copper, iron, mercury, silver, cadmium, tin, lead, antimony, bismuth, thallium, chromium, molybdenum, cobalt, nickel, tungsten, sodium, calcium, magnesium, manganese and arsenic. In a preferred embodiment of the invention, the metal is selected from zinc, molybdenum, antimony, preferably zinc and molybdenum, preferably zinc. Mixtures of metals can be used. The metal dithiophosphates are neutral as exemplified in Formula (IV-d) or basic when a stoichiometric excess of metal is present.

In another preferred embodiment of the invention, R₂₅ and R₂₆ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 2 to 24 carbon atoms, more preferentially from 3 to 18 carbon atoms, even more preferentially from 5 to 12 carbon atoms. In another preferred embodiment of the invention, R₂₅ and R₂₆ represent independently of each other unsubstituted hydrocarbon-containing groups, said hydrocarbon-containing groups being able to be alkyl, alkenyl, alkynyl, aryl, preferably phenyl or benzyl groups. In another preferred embodiment of the invention, R₂₅ and R₂₆ represent independently of each other linear or branched alkyl hydrocarbon-containing groups, more preferentially linear alkyl hydrocarbon-containing groups. In another preferred embodiment of the invention, R₂₅ and R₂₆ represent independently of each other hydrocarbon-containing groups optionally substituted with one or more oxygen, nitrogen, sulphur and/or phosphorus atoms, preferably with one or more oxygen atoms.

The useable metal dithiophosphates are compounds well known to a person skilled in the art. Commercial compounds are for example Additin® RC 3038, Additin® RC 3045, Additin® RC 3048, Additin® RC 3058, Additin® RC 3080, Additin® RC 3180, Additin® RC 3212, Additin® RC 3580 marketed by the company Rhein Chemie, Kikulube® Z112 marketed by the company Adeka, Lubrizol® 1371, Lubrizol® 1375, Lubrizol® 1395, Lubrizol® 5179 marketed by the company Lubrizol, Oloa® 260 or Oloa® 267 marketed by the company Oronite.

In a preferred embodiment of the invention, the metal dithiophosphate is a molybdenum dithiophosphate of Formula (IV-d-1), wherein R₂₅ and R₂₆ have the same meaning as in Formula (IV-d):

In another preferred embodiment of the invention, the metal dithiophosphate is a zinc dithiophosphate of Formula (IV-d-2), wherein R₂₅ and R₂₆ have the same meaning as in Formula (IV-d):

In an embodiment of the invention, the lubricating composition comprises from 0.1 to 5% by mass of dithiophosphate, relative to the total mass of the lubricating composition, preferably from 0.2 to 4%, more preferentially from 0.3 to 2%, even more preferentially from 0.5 to 1%.

Thiadiazole

The lubricating composition according to the invention comprises at least one compound D comprising a thiadiazole group. With a view to simplification of the description, compound D comprising a thiadiazole group is called “thiadiazole” in the remainder of the present description. In an embodiment of the invention, the thiadiazole is a compound of Formula (V-a)

wherein:

-   -   R₂₇ and R₂₈, identical or different, represent independently a         hydrogen atom or a linear or branched, saturated or unsaturated,         alkyl group, comprising from 1 to 30 carbon atoms,     -   a represents an integer ranging from 1 to 3,     -   b represents an integer ranging from 1 to 3.

In another embodiment of the invention, R₂₇ and R₂₈ represent a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 20 carbon atoms, preferentially from 1 to 15 carbon atoms, more preferentially from 5 to 15 carbon atoms, advantageously from 10 to 15 carbon atoms. In a preferred embodiment of the invention, R₂₇ and R₂₈ represent a linear or branched, saturated alkyl group, comprising 12 carbon atoms. In another preferred embodiment of the invention, a represents an integer equal to 1 or 2 and b represents an integer equal to 1 or 2.

In another embodiment of the invention, the thiadiazole is a compound of Formula (V-b)

wherein:

-   -   R₂₈ represents a hydrogen atom or a linear or branched,         saturated or unsaturated, alkyl group, comprising from 1 to 30         carbon atoms,     -   b represents an integer ranging from 1 to 3.

In another embodiment of the invention, R₂₈ represents a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 20 carbon atoms, preferentially from 1 to 15 carbon atoms, more preferentially from 5 to 15 carbon atoms, advantageously from 10 to 15 carbon atoms. In a preferred embodiment of the invention, R₂₈ represents a linear or branched, saturated alkyl group, comprising 12 carbon atoms. In another preferred embodiment of the invention, b represents an integer equal to 1 or 2. In another preferred embodiment of the invention, the thiazole is a mixture of at least one compound of Formula (V-a) and at least one compound of Formula (V-b) as defined above.

In a more preferred embodiment of the invention, the thiazole is a mixture of:

-   -   at least one compound of Formula (V-a) wherein R₂₇ and R₂₈         represent a linear or branched, saturated alkyl group,         comprising 12 carbon atoms, a represents an integer equal to 1         or 2 and b represents an integer equal to 1 or 2;     -   at least one compound of Formula (V-b) wherein R₂₈ represents a         linear or branched, saturated alkyl group, comprising 12 carbon         atoms and b represents an integer equal to 1 or 2.

As examples of thiadiazole according to the invention, the product RC 8210 marketed by the company Rhein Chemie may be mentioned. In an embodiment of the invention, the lubricating composition comprises from 0.1 to 5% by mass of thiadiazole, relative to the total mass of the lubricating composition, preferably from 0.2 to 4%, more preferentially from 0.3 to 2%, even more preferentially from 0.5 to 1%. In another embodiment of the invention, the ratio by weight (compound comprising a dithiophosphate group: compound comprising a thiadiazole group) ranges from 3:1 to 1:8, preferably from 2:1 to 1:5, advantageously from 1:1 to 1:5.

Base Oil

The lubricating compositions according to the invention can contain any type of lubricating base oil, mineral, synthetic or natural, animal or vegetable, suited to their use. The base oil or oils used in the lubricating compositions according to the present invention can be oils of mineral or synthetic origin of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) as summarized below, alone or in a mixture.

TABLE I Saturates Sulphur Viscosity content content Index (VI) Group I Mineral <90% >0.03% 80 ≦ VI < 120 oils Group II ≧90% ≦0.03% 80 ≦ VI < 120 Hydrocracked oils Group III ≧90% ≦0.03% ≧120 Hydrocracked or hydro- isomerized oils Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in bases of groups I to IV

The mineral base oils according to the invention include all types of bases obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization, hydrofinishing. The base oils of the lubricating compositions according to the invention can also be synthetic oils, such as certain esters of carboxylic acids and alcohols, or polyalphaolefins. The polyalphaolefins used as base oils are for example obtained from monomers having 4 to 32 carbon atoms (for example octene, decene), and a viscosity at 100° C. comprised between 1.5 and 15 cSt measured according to the standard ASTM D445. Their weight-average molecular weight is typically comprised between 250 and 3000 measured according to the standard ASTM D5296. Mixtures of synthetic oils and minerals can also be used.

There is no limitation as regards the use of a specific lubricating base for producing the lubricating compositions according to the invention, except that they must have properties, in particular in terms of viscosity, viscosity index, sulphur content, oxidation resistance, suitable for use in a gearbox, in particular in a motor vehicle gearbox, in particular in a manual gearbox. In an embodiment of the invention, the lubricating bases represent at least 50% by mass, relative to the total mass of the lubricating composition, preferentially at least 60%, or also at least 70%. Typically, they represent between 75 and 99.9% by mass, relative to the total mass of the lubricating compositions according to the invention.

In a preferred embodiment of the invention, the lubricating compositions according to the invention comprise mineral bases of group I and/or III, or synthetic bases of group IV according to the API classification. In another preferred embodiment of the invention, the lubricating compositions have a kinematic viscosity at 100° C. measured according to the standard ASTM D445 comprised between 4 and 41 cSt, according to the SAE J 306 classification, preferably between 4.1 and 32.5 cSt, advantageously from 6 to 18.5 cSt. The preferred grades are all the grades comprised between grades 75W and 140, in particular grades 75W, 75W80 and 75W90. In another preferred embodiment of the invention, the lubricating compositions have a viscosity index (VI) greater than 120 (standard ASTM 2270).

Other Additives

The lubricating compositions according to the invention can also contain all types of additives suitable for use in the formulations of oils for transmissions, for example one or more additives selected from the polymers, antioxidants, -corrosion-inhibiting additives, and dispersants, present at the usual levels required for the application. The polymers are selected from the group of shear-stable polymers, preferably from the group constituted by the ethylene and alpha-olefin copolymers, the polyacrylates such as the polymethacrylates, olefin copolymers (OCP), Ethylene Propylene Diene Monomers (EPDM), polybutenes, styrene and olefin copolymers, hydrogenated or not, or styrene and acrylate copolymers. The preferred polymers are the polymethacrylates (PMA).

In a preferred embodiment of the invention, the lubricating composition also comprises at least one dispersant. The preferred dispersants are the polyisobutylenes (PIB) or polyisobutene derivatives. More preferentially, the lubricating composition according to the invention can comprise a dispersant derived from polyisobutene. As examples of polyisobutene derivatives, the polyisobutylene succinic anhydrides, amine-containing derivatives of polyisobutylene of succinic anhydride (PIB succinimides) may be mentioned.

The preferred antioxidants are for example amine-containing antioxidants. More preferentially, the lubricating composition according to the invention can comprise an antioxidant selected from the group of the aromatic amines, such as for example the diphenylamines, in particular dialkylphenylamines, such as the octadiphenylamines, phenyl-alpha-naphthyl amines.

In another embodiment of the invention, the lubricating composition can comprise an antioxidant derived from phenol (dibutylhydroxytoluene BHT and derivatives) or a sulphur-containing antioxidant (sulphurized phenates). In a preferred embodiment of the invention, the lubricating composition comprises an antioxidant selected from the group formed by the aromatic amines or phenol derivatives. The preferred corrosion-inhibiting additives are phenol derivatives, in particular ethoxylated phenol derivatives and substituted with alkyl groups in the ortho position. In another preferred embodiment, the lubricating composition also comprises at least one dispersant and at least one other additive selected from those mentioned above.

In an embodiment of the invention, the lubricating composition comprises:

-   -   from 75 to 99.6% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II) as described above,     -   from 0.1 to 5% of a compound D comprising a thiadiazole group,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In another embodiment of the invention, the lubricating composition comprises:

-   -   from 75 to 99.6% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II-a) as described above,     -   from 0.1 to 5% of a compound D comprising a thiadiazole group,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In another embodiment of the invention, the lubricating composition comprises:

-   -   from 75 to 99.1% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II) as described above,     -   from 0.1 to 5% of at least one compound D comprising a         thiadiazole group,     -   from 0.5 to 3% of at least one other additive,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In another embodiment of the invention, the lubricating composition comprises:

-   -   from 75 to 99.1% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II-a) as described above,     -   from 0.1 to 5% of a compound D comprising a thiadiazole group,     -   from 0.5 to 3% of another additive,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In another embodiment of the invention, the lubricating composition essentially consists of:

-   -   75 to 99.6% of a base oil,     -   0.1 to 5% of a compound B comprising a phosphite group,     -   0.1 to 5% of a compound C comprising a dithiophosphate group,     -   0.1 to 5% of a compound A comprising a dithiocarbamate group,         this compound being a mixture of an amine dithiocarbamate of         general formula (I) as described above and a metal         dithiocarbamate of general formula (II) as described above,     -   0.1 to 5% of a compound D comprising a thiadiazole group,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In another embodiment of the invention, the lubricating composition essentially consists of:

-   -   from 75 to 99.6% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II-a) as described above,     -   from 0.1 to 5% of a compound D comprising a thiadiazole group,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In an embodiment of the invention, the lubricating composition essentially consists of:

-   -   from 75 to 99.1% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II) as described above,     -   from 0.1 to 5% of a compound D comprising a thiadiazole group,     -   from 0.5 to 3% of another additive,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In an embodiment of the invention, the lubricating composition essentially consists of:

-   -   from 75 to 99.1% of a base oil,     -   from 0.1 to 5% of a compound B comprising a phosphite group,     -   from 0.1 to 5% of a compound C comprising a dithiophosphate         group,     -   from 0.1 to 5% of a compound A comprising a dithiocarbamate         group, this compound being a mixture of an amine dithiocarbamate         of general formula (I) as described above and a metal         dithiocarbamate of general formula (II-a) as described above,     -   from 0.1 to 5% of a compound D comprising a thiadiazole group,     -   from 0.5 to 3% of another additive,     -   the ratio by weight (compound C comprising a dithiophosphate         group: compound D comprising a thiadiazole group) ranging from         5:1 to 1:10.

In the embodiments as described above, the percentages are expressed by mass relative to the total mass of the lubricating composition. All of the characteristics and preferences presented for the base oil, the compound comprising a phosphite group, the compound comprising a thiophosphate group, the compound comprising a dithiocarbamate group, the compound comprising a thiadiazole group and the additional additive also apply to the above lubricating compositions. In an embodiment of the invention, the lubricating composition is not an emulsion. In another embodiment of the invention, the lubricating composition is an anhydrous composition. An object of the invention is also a method for preparing a lubricating composition as defined above.

In an embodiment of the invention, the method comprises at least the following steps:

-   -   (a) mixing at least one compound comprising a thiadiazole group,         at least one base oil and at least one dispersant under stirring         and at a temperature of at least 40° C. for at least 30 min,     -   (b) addition of at least one compound comprising a phosphite         group, at least one compound comprising a dithiophosphate group         and at least one compound comprising a dithiocarbamate group,         this compound being a mixture of at least one amine         dithiocarbamate of general formula (I) as described above and at         least one metal dithiocarbamate of general formula (II) as         described above, under stirring and at a temperature of at least         40° C. for at least 1 h,     -   (c) addition of at least one base oil.

In an embodiment, the temperature of step (a) ranges from 40 to 70° C. In another embodiment, the temperature of step (b) ranges from 40 to 70° C. In a preferred embodiment of the invention, step (b) also comprises the addition of at least one additional additive.

In another preferred embodiment of the invention, the base oil of step (c) is identical to that of step (a). In another preferred embodiment of the invention, the base oil of step (c) is different from that of step (a). All of the characteristics and preferences presented for the base oil, the compound comprising a phosphite group, the compound comprising a thiophosphate group, the compound comprising a dithiocarbamate group, the compound comprising a thiadiazole group, the dispersant and the additional additive also apply to the above method.

An object of the invention is also the use of a lubricating composition as defined above for the lubrication of transmissions such as the gearboxes, the axles, preferably manual gearboxes of motor vehicles. In an embodiment, an object of the invention is the use of a lubricating composition as defined above for the lubrication of a mechanical part in brass, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox. In a preferred embodiment, an object of the invention is the use of a lubricating composition as defined above for the lubrication of synchronizers present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox.

An object of the invention is also the use of a lubricating composition as defined above for reducing the fuel consumption of vehicles, in particular of motor vehicles. An object of the invention is also the use of a lubricating composition as defined above for reducing the wear of gearbox synchronizers, preferentially of manual gearboxes. An object of the invention is also the use of a lubricating composition as defined above for reducing the flaking of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox.

All of the characteristics and preferences presented for the lubricating composition also apply to the above uses. An object of the invention is also a method for lubricating transmissions such as the gearboxes, the axles, preferably manual gearboxes of motor vehicles, said method comprising at least one step of bringing a lubricating composition as defined above into contact with the transmissions. In an embodiment, an object of the invention is a method for lubricating a mechanical part made of brass, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox.

In a preferred embodiment, an object of the invention is a method for lubricating synchronizers present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox. An object of the invention is also a method for reducing the seizing of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox, comprising at least bringing the mechanical part into contact with a lubricating composition as defined above. An object of the invention is also a method for reducing the wear of a gearbox synchronizer, preferentially of manual gearboxes, comprising at least bringing the synchronizer in contact with a lubricating composition as defined above.

An object of the invention is also a method for reducing the flaking of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox, comprising at least bringing the mechanical part into contact with a lubricating composition as defined above. An object of the invention is also a method for reducing the seizing, wear and flaking of a mechanical part, preferentially present in a transmission component, more preferentially in a gearbox, even more preferentially in a manual gearbox, said method comprising at least one step of bringing the mechanical part into contact with a lubricating composition as defined above. In an embodiment of the method of the invention, the mechanical part is a synchronization device (synchronizer). All of the characteristics and preferences presented for the lubricating composition also apply to the above methods.

An object of the invention is also the use of at least one compound A comprising a dithiocarbamate group, at least one compound B comprising a phosphite group, at least one compound C comprising a dithiophosphate group and at least one compound D comprising a thiadiazole group in a base oil for improving the wear, extreme-pressure, friction and anti-seizing properties of a lubricating composition, compound A comprising a dithiocarbamate group being a mixture of:

-   -   at least one amine dithiocarbamate of general formula (I)         (compound

wherein

-   -   R₁ and R₂ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms,     -   R₃, R₄ and R₅ represent independently of each other a hydrogen         atom or a hydrocarbon-containing group of 1 to 30 carbon atoms,         it being understood that at least one of the R₃, R₄ and R₅         groups is not a hydrogen atom, and         -   at least one metal dithiocarbamate of general formula (II)             (compound A-2)

-   -   wherein R₆ and R₇ represent independently of each other         hydrocarbon-containing groups, optionally substituted,         comprising from 1 to 30 carbon atoms, M represents a metal         cation and n is the valency of this metal cation, and     -   compound D comprising a thiadiazole group being selected from         the group formed by         -   a compound of Formula (V-a)

wherein:

-   -   R₂₇ and R₂₈, identical or different, represent independently a         hydrogen atom or a linear or branched, saturated or unsaturated,         alkyl group, comprising from 1 to 30 carbon atoms,     -   a represents an integer ranging from 1 to 3,     -   b represents an integer ranging from 1 to 3,         -   a compound of Formula (V-b)

wherein

-   -   R₂₈ represents a hydrogen atom or a linear or branched,         saturated or unsaturated, alkyl group, comprising from 1 to 30         carbon atoms,     -   b represents an integer ranging from 1 to 3,         -   a mixture of at least one compound of Formula (V-a) and at             least one compound of Formula (V-b).

All of the characteristics and preferences presented for the base oil, the compound comprising a phosphite group, the compound comprising a thiophosphate group, the compound comprising a dithiocarbamate group and the compound comprising a thiadiazole group also apply to the above use. The use of these five additives in a lubricating composition makes it possible to simultaneously reduce wear, improve the extreme-pressure properties, reduce the coefficient of friction and improve the anti-seizing properties of the lubricating composition. The use of these five additives in a lubricating composition also makes it possible to retain good anti-flaking properties of the lubricating composition.

An object of the invention is also a composition of the additives-concentrate type comprising at least one compound A comprising a dithiocarbamate group, at least one compound B comprising a phosphite group, at least one compound C comprising a dithiophosphate group and at least one compound D comprising a thiadiazole group. All of the characteristics and preferences presented for compound A comprising a dithiocarbamate group, for compound B comprising a phosphite group, for compound C comprising a thiophosphate group and compound D comprising a thiadiazole group also apply to the composition of the additives-concentrate type above.

The different objects of the present invention and the implementation thereof will be better understood on reading the following examples. These examples are given by way of indication, without being limitative in nature.

Examples

Lubricating compositions No. 1 to No. 7 are prepared from the following components

-   -   a group IV base oil of PAO type having a viscosity at 100° C. of         6 cSt measured according to the standard ASTM D445, and         viscosity index equal to 125 measured according to the standard         ASTM 2270,     -   a dithiocarbamate marketed under the name Vanlube EZ by the         company Vanderbilt, which is a mixture of:         -   zinc diamyldithiocarbamate of formula:

-   -   -   and diamyl amine diamyldithiocarbamate of formula:

-   -   a phosphite which is the di-n-octyl phosphite marketed under the         name Irgafos OPH by the company BASF,     -   a dithiophosphate,         3-[(bis-isopropyloxyphosphinothioyl)thio]propionic acid ethyl         ester marketed under the name Irgalube 63 by the company BASF,     -   a dimercaptothiadiazole derivative marketed under the name RC         8210 by the company Rhein Chemie,     -   a dispersant which is a derivative of the polyisobutylene         succinimide marketed under the name Doversperse H1015-P by the         company DoverChemical,     -   an antioxidant which is a diphenyl amine marketed under the name         Irganox L57 by the company BASF,     -   a corrosion inhibitor A1 which is a benzotriazole marketed under         the name RC 5800 by the company Rhein Chemie,     -   a corrosion inhibitor A2 which is a mixture of a C₁₂-C₁₆ alcohol         and an alkyl ether carboxylic acid, the content by weight of         alcohol being at most 20% relative to the total weight of the         mixture and the content by weight of alkyl ether being at least         70% relative to the total weight of the mixture (Irgacor 843         marketed by the company BASF).

Lubricating compositions No. 1 to 7 are described in Table II: the percentages given are percentages by mass.

TABLE II Lubricating composition No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 Base oil 96 95.5 95.5 95.5 96.8 96.9 96.9 Dithiocarbamate 1 1 1 1 1 0.7 1 Phosphite 1 1 1 1 0.5 1 0.7 Dithiophosphate 1 1 1 1 0.2 0.4 0.4 Thiadiazole (—) (—) (—) 0.5 0.7 (—) (—) Corrosion inhibitor A1 (—) 0.5 (—) (—) (—) (—) (—) Corrosion inhibitor A2 (—) (—) 0.5 (—) (—) (—) (—) Dispersant 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Antioxidant 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Lubricating compositions No. 1 to No. 3 and No. 6 to No. 7 are comparative compositions; lubricating compositions No. 4 and No. 5 are according to the invention.

Test No. 1: Evaluation of the Anti-Wear Properties of Lubricating Compositions on Gearbox Synchronizers

The objective of this test is to evaluate the anti-wear properties of lubricating compositions vis-à-vis synchronizers. The synchronizer wear tests on lubricating compositions 1 to 5 were carried out on a cone-ring pair under the following conditions (procedure SYNC-13, SAE 2-A)):

-   -   Threaded brass ring of 54 mm (for example reference 7700 708 152         or 7700 869 430,     -   Cone of idler pinion gear box JXX, stoned rectified carbonitride         steel (for example reference 7700 867 612 or 7700 740 880,     -   Oil: 125 ml of the lubricating composition to be tested, oil         level on the lower portion of the ring     -   SAE2/A Machine SAE/2 synchro adapter     -   I=0.155 m2/kg     -   N=600 rpm     -   F=60 daN     -   T=3.5 s (consecutive period between 2 consecutive braking         operations)     -   n=20,000 gear changing cycles (20 hours)

At the end of these 20,000 cycles; the axial wear of the synchronizer ring/gear cone pair is measured in mm. This test more particularly makes it possible to evaluate the anti-wear properties of a lubricating composition in steel/brass surface contacts, corresponding to the type of contacts utilized in the synchronizers. The results of the anti-wear properties of lubricating compositions 1 to 5 on the synchronizers are described in Table III; the lower the value obtained, the better the anti-wear properties vis-à-vis synchronizers.

TABLE III Lubricating composition 1 2 3 4 5 Synchronizer wear in 0.9 0.9 0.9 0.7 0.3 mm

The results show that lubricating composition No. 4 according to the invention makes it possible to significantly reduce the wear of the synchronizers relative to a lubricating composition comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite but comprising no thiadiazole (composition No. 1) or relative to lubricating compositions comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite as well as a corrosion inhibitor different from a thiadiazole (compositions No. 2 and No. 3). Furthermore, the results relating to lubricating composition No. 5 according to the invention show a very clear reduction in the wear of the synchronizers relative to a lubricating composition comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite but comprising no thiadiazole (composition No. 1) or relative to lubricating compositions comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite as well as a corrosion inhibitor different from a thiadiazole (compositions No. 2 and No. 3), thus demonstrating that a lubricating composition according to the invention has very good anti-wear properties vis-à-vis the synchronizers.

Test No. 2: Evaluation of the Anti-Wear Properties of a Composition According to the Invention on Gearbox Synchronizers

The objective of this test is to confirm the anti-wear properties of a lubricating composition according to the invention vis-à-vis synchronizers. For this, a synchronizer blocking test was carried out with lubricating composition No. 5 on a cone-ring pair under the following conditions (procedure SYNC-40):

-   -   Threaded brass ring of 54 mm (for example reference 7700 708 152         or 7700 869 430)     -   Cone of idler pinion gear box JXX, stoned rectified carbonitride         steel (for example reference 7700 867 612 or 7700 740 880)     -   Oil: 250 ml of lubricating composition No. 5, oil level in the         middle of the pinion and the ring     -   SAE2/A Machine SAE/2 synchro adapter     -   I=0.155 m²/kg     -   N=300 rpm     -   F=60 daN     -   T=6 s (consecutive period between 2 consecutive braking         operations)     -   n=10,125 gear changing cycles (21 hours)

The synchronizer blocking test is considered satisfactory if, during the 10,125 gear changing cycles, the number of cycles where the disengagement between the cone and the ring requires the application of a counter-torque greater than 2 mN is at most 100 cycles. The result of the test with lubricating composition No. 5 is 32, which confirms the very good anti-wear properties of this lubricating composition according to the invention vis-à-vis synchronizers.

Test No. 3: Evaluation of the Anti-Wear and Extreme-Pressure Properties of the Lubricating Compositions

The objective of this test is to evaluate the anti-wear and extreme-pressure properties of lubricating compositions. The anti-wear properties of lubricating compositions No. 1, No. 5, No. 6 and No. 7 were evaluated by means of a 4 ball wear test according to the standard D55 1078; this test using steel balls in particular; a value greater than 0.8 mm corresponding to a level of wear which is not acceptable. This test more particularly makes it possible to evaluate the anti-wear properties of a lubricating composition in steel/steel surface contacts, corresponding to the majority of the contacts utilized in a gearbox.

The extreme-pressure properties of lubricating compositions No. 1, No. 5, No. 6 and No. 7 were evaluated by means of a 4 ball wear test according to the standard D55 1136; a value less than 90 daN corresponding to extreme-pressure properties which are not acceptable. The results of these tests are described in Table V.

TABLE V Lubricating composition 1 5 6 7 Wear (4 ball test) in mm 0.42 0.72 0.41 0.42 Extreme-pressure (4 ball 110 90 70 70 test) in daN

The results show that a lubricating composition according to the invention (composition No. 5) has anti-wear and extreme-pressure properties that are satisfactory, or even improved relative to compositions comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite according to the invention but comprising no thiadiazole (compositions No. 1, No. 6 and No. 7).

Test No. 4: Evaluation of the Anti-Seizing Properties of Lubricating Compositions

The objective of this test is to evaluate the anti-seizing properties of lubricating compositions. The anti-seizing properties of lubricating compositions No. 1, No. 5, No. 6 and No. 7 were evaluated by means of an FZG test according to the standard CEC L84 (A/16, 6R/120); the higher the value obtained at the end of the test, the better the anti-seizing properties. The results of this test with compositions No. 1, No. 5, No. 6 and No. 7 are described in Table VI.

TABLE VI Lubricating composition 1 5 6 7 Anti-seizing 10 10 7 7

The results show that a lubricating composition according to the invention (composition No. 5) has anti-seizing properties which are equivalent, or even improved relative to lubricating compositions comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite but comprising no thiadiazole (compositions No. 1, No. 6 and No. 7).

Test No. 5: Evaluation of the Anti-Flaking Properties of Lubricating Compositions

The objective of this test is to evaluate the anti-flaking properties of lubricating compositions. For this, a FZG C6 test was carried out with lubricating compositions No. 1, No. 5, No. 6 and No. 7. The objective of this test is to evaluate the ability of a lubricating composition to protect gear surfaces against damage by flaking (pitting).

Gears of the PT-C type were used and tested on an FZG machine. A constant rotation rate was fixed at 1440 rpm, also with a constant load (level 9). The temperature of the lubricating composition to be tested was set at 120° C. The test was then “run” initially for 8 h, then once the first grooves appeared on the teeth, the duration of these “runs” was reduced.

The final aim is to determine the lifetime of a pinion lubricated with lubricating composition by evaluating the flaked surface on each tooth of the pinion. The failure criterion is reached when the surface comprising flakes for all of the teeth ≧1 mm². The results are described in Table VII and are expressed in hours; the higher the value obtained, the longer the time before flakes appear on the surface of the pinion and therefore the better the anti-flaking properties.

TABLE VII Lubricating composition 1 5 6 7 Flaking 32 32 24 25

The results show that a lubricating composition according to the invention (composition No. 5) has anti-flaking properties which are equivalent, or even improved relative to lubricating compositions comprising a combination of a dithiocarbamate, a dithiophosphate and a phosphite but comprising no thiadiazole (compositions No. 1, No. 6 and No. 7). 

1. A lubricating composition comprising: at least one base oil; at least one compound A comprising a dithiocarbamate group; at least one compound B comprising a phosphite group; at least one compound C comprising a dithiophosphate group; and at least one compound D comprising a thiadiazole group; compound A comprising a dithiocarbamate group being a mixture: of at least one amine dithiocarbamate of general formula (I) (compound A-1)

wherein R₁ and R₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms; R₃, R₄ and R₅ represent independently of each other a hydrogen atom or a hydrocarbon-containing group of 1 to 30 carbon atoms, it being understood that at least one of the R₃, R₄ and R₅ groups is not a hydrogen atom; and of at least one metal dithiocarbamate of general formula (II) (compound A-2),

wherein R₆ and R₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, M represents a metal cation and n is the valency of this metal cation; compound D comprising a thiadiazole group being selected from the group formed by: a compound of Formula (V-a)

wherein: R₂₇ and R₂₈, identical or different, represent independently a hydrogen atom or a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 30 carbon atoms; a represents an integer ranging from 1 to 3, b represents an integer ranging from 1 to 3, a compound of Formula (V-b)

wherein R₂₈ represents a hydrogen atom or a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 30 carbon atoms; b represents an integer ranging from 1 to 3; a mixture of at least one compound of Formula (V-a) and at least one compound of Formula (V-b); and the ratio by weight (compound comprising a dithiophosphate group: compound comprising a thiadiazole group) ranging from 5:1 to 1:10.
 2. The lubricating composition according to claim 1 wherein compound A comprising a dithiocarbamate group is a mixture of: at least one amine dithiocarbamate of general formula (I)

wherein R₁ and R₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms; R₃, R₄ and R₅ represent independently of each other a hydrogen atom or a hydrocarbon-containing group of 1 to 30 carbon atoms, it being understood that at least one of the R₃, R₄ and R₅ groups is not a hydrogen atom; and at least one metal dithiocarbamate of general formula (II-a),

wherein R₆ and R₇ represent independently of each other linear alkyl hydrocarbon-containing groups.
 3. The lubricating composition according to claim 2 wherein R₆ and R₇ represent independently of each other linear alkyl groups comprising from 4 to 12 carbon atoms.
 4. The lubricating composition according to claim 1 comprising from 0.1 to 5% by mass of compounds A comprising a dithiocarbamate group, relative to the total mass of lubricating composition.
 5. The lubricating composition according to claim 1 comprising from 0.1 to 3% by mass of the mixture of amine dithiocarbamate corresponding to Formula (I) (compound A-1) and metal dithiocarbamate corresponding to Formula (II) (compound A-2) relative to the total mass of the composition.
 6. The lubricating composition claim 1 wherein compound B comprising a phosphite group is selected from the phosphite monoesters, the phosphite diesters or the phosphite triesters, used alone or in a mixture.
 7. The lubricating composition claim 1 comprising from 0.1 to 5% by mass of compound B comprising a phosphite group, relative to the total mass of lubricating composition.
 8. The lubricating composition claim 1 wherein compound C comprising a dithiophosphate group is selected from the group constituted by the ammonium dithiophosphates, amine dithiophosphates, ester dithiophosphates and metal dithiophosphates, used alone or in a mixture.
 9. The lubricating composition claim 1 comprising from 0.1 to 5% by mass of compound C comprising a dithiophosphate group, relative to the total mass of lubricating composition.
 10. The lubricating composition according to claim 1 comprising from 0.1 to 5% by mass of compound D comprising a thiadiazole group, relative to the total mass of the lubricating composition.
 11. The lubricating composition according to claim 1 wherein the ratio by weight (compound C comprising a dithiophosphate group: compound D comprising a thiadiazole group) ranges from 3:1 to 1:8.
 12. The lubricating composition according to claim 1 also comprising an antioxidant selected from the group formed by the aromatic amines or phenol derivatives.
 13. The lubricating composition according to claim 1 also comprising a dispersant derived from polyisobutene.
 14. The lubricating composition according to claim 1 having a kinematic viscosity at 100° C. according to the standard ASTM D445 comprised between 4 and 40 cSt.
 15. A method for lubricating transmissions, comprising bringing the transmissions into contact with a lubricating composition comprising at least one base oil; at least one compound A comprising a dithiocarbamate group; at least one compound B comprising a phosphite group; at least one compound C comprising a dithiophosphate group; and at least one compound D comprising a thiadiazole group; compound A comprising a dithiocarbamate group being a mixture: of at least one amine dithiocarbamate of general formula (I) (compound A-1)

wherein R₁ and R₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms; R₃, R₄ and R₅ represent independently of each other a hydrogen atom or a hydrocarbon-containing group of 1 to 30 carbon atoms, it being understood that at least one of the R₃, R₄ and R₅ groups is not a hydrogen atom; and of at least one metal dithiocarbamate of general formula (II) (compound A-2),

wherein R₆ and R₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, M represents a metal cation and n is the valency of this metal cation; compound D comprising a thiadiazole group being selected from the group formed by: a compound of Formula (V-a)

wherein: R₂₇ and R₂₈, identical or different represent independently a hydrogen atom or a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 30 carbon atoms; a represents an integer ranging from 1 to 3, b represents an integer ranging from 1 to 3, a compound of Formula (V-b)

wherein R₂₈ represents a hydrogen atom or a linear or branched saturated or unsaturated, alkyl group, comprising from 1 to 30 carbon atoms; b represents an integer ranging from 1 to 3; a mixture of at least one compound of Formula (V-a) and at least one compound of Formula (V-b); and the ratio by weight (compound comprising a dithiophosphate group: compound comprising a thiadiazole group) ranging from 5:1 to 1:10.
 16. A method for reducing the fuel consumption of vehicles, comprising bringing a mechanical part of the vehicle engine into contact with a lubricating composition according to claim
 1. 17. (canceled)
 18. A method for improving the anti-wear, extreme-pressure, friction and anti-seizing properties of a lubricating composition, comprising adding at least one compound A comprising a dithiocarbamate group, at least one compound B comprising a phosphite group, at least one compound C comprising a dithiophosphate group and at least one compound D comprising a thiadiazole group into a base oil compound A comprising a dithiocarbamate group being a mixture of: at least one amine dithiocarbamate of general formula (I) (compound A-1)

wherein R₁ and R₂ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms; R₃, R₄ and R₅ represent independently of each other a hydrogen atom or a hydrocarbon-containing group of 1 to 30 carbon atoms, it being understood that at least one of the R₃, R₄ and R₅ groups is not a hydrogen atom; and at least one metal dithiocarbamate of general formula (II) (compound A-2),

wherein R₆ and R₇ represent independently of each other hydrocarbon-containing groups, optionally substituted, comprising from 1 to 30 carbon atoms, M represents a metal cation and n is the valency of this metal cation; compound D comprising a thiadiazole group being selected from the group formed by: a compound of Formula (V-a)

wherein: R₂₇ and R₂₈, identical or different, represent independently a hydrogen atom or a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 30 carbon atoms; a represents an integer ranging from 1 to 3; b represents an integer ranging from 1 to 3; a compound of Formula (V-b)

wherein R₂₈ represents a hydrogen atom or a linear or branched, saturated or unsaturated, alkyl group, comprising from 1 to 30 carbon atoms; and b represents an integer ranging from 1 to 3; a mixture of at least one compound of Formula (V-a) and at least one compound of Formula (V-b). 